Abstract

Small signal gain measurements of optically excited terahertz silicon lasers are reported. Two types of lasers, Si:P and Si:Bi, were investigated. They were optically excited with radiation from a free electron laser or a laser. The experiments were performed with an oscillator-amplifier scheme where one sample serves as a laser while the other one is an amplifier. In case of the free electron laser the pump frequency corresponds to intracenter excitation of the or states of the P and Bi Coulomb centers, and the gain was determined for the , transitions in Si:P and the transition in Si:Bi. Pumping with a laser leads to photoexcitation of the Coulomb centers. In this case the gain was determined for the of Si:P transition. The gain for intracenter pumping is in the range while for photoexcitation the gain is considerably less, namely . The experimental results are analyzed and found to be in good agreement with theoretical calculations based on balance equations.

Received 27 July 2007Accepted 13 September 2007Published online 07 November 2007

Acknowledgments:

We gratefully acknowledge the support by the Stichting voor Fundamenteel Onderzoek der Materie (FOM) in providing the required beam time on FELIX and highly appreciate the skilful assistance by the FELIX staff. This work was supported by the Deutsche Forschungsgemeinschaft (DFG) and the Russian Foundation for Basic Research (RFBR), RFBR Grant Nos. 05-02-16790 and 05-02-16734.